diff --git a/MicroBenchmarks/XRay/CMakeLists.txt b/MicroBenchmarks/XRay/CMakeLists.txt
--- a/MicroBenchmarks/XRay/CMakeLists.txt
+++ b/MicroBenchmarks/XRay/CMakeLists.txt
@@ -1,8 +1,13 @@
-add_subdirectory(ReturnReference)
-if(NOT TARGET_OS STREQUAL "Darwin")
-  # FDRMode test is failing on Darwin because
-  # `__xray_log_select_mode("xray-fdr")` returns `XRAY_MODE_NOT_FOUND`.
-  #
-  # Disable the test until it is fixed. rdar://problem/44578416
+include(CheckIncludeFiles)
+
+check_cxx_compiler_flag(-fxray-instrument COMPILER_HAS_FXRAY_INSTRUMENT)
+check_include_files("xray/xray_interface.h" HAVE_XRAY_INTERFACE_INCLUDE LANGUAGE CXX)
+
+if(COMPILER_HAS_FXRAY_INSTRUMENT AND HAVE_XRAY_INTERFACE_INCLUDE AND ARCH STREQUAL "x86" AND NOT TARGET_OS STREQUAL "Darwin")
+  message(STATUS "XRay tests enabled")
+
+  add_subdirectory(ReturnReference)
   add_subdirectory(FDRMode)
+else()
+  message(STATUS "Compiler does not support XRay; tests disabled")
 endif()
diff --git a/MicroBenchmarks/XRay/FDRMode/CMakeLists.txt b/MicroBenchmarks/XRay/FDRMode/CMakeLists.txt
--- a/MicroBenchmarks/XRay/FDRMode/CMakeLists.txt
+++ b/MicroBenchmarks/XRay/FDRMode/CMakeLists.txt
@@ -1,8 +1,8 @@
-check_cxx_compiler_flag(-fxray-instrument COMPILER_HAS_FXRAY_INSTRUMENT)
-if(ARCH STREQUAL "x86" AND COMPILER_HAS_FXRAY_INSTRUMENT)
-  list(APPEND CPPFLAGS -std=c++11 -Wl,--gc-sections -fxray-instrument)
-  list(APPEND LDFLAGS -fxray-instrument)
-  llvm_test_run()
-  llvm_test_executable(fdrmode-bench fdrmode-bench.cc)
-  target_link_libraries(fdrmode-bench benchmark)
-endif()
+# FDRMode test is failing on Darwin because
+# `__xray_log_select_mode("xray-fdr")` returns `XRAY_MODE_NOT_FOUND`.
+
+list(APPEND CPPFLAGS -std=c++11 -Wl,--gc-sections -fxray-instrument)
+list(APPEND LDFLAGS -fxray-instrument)
+llvm_test_run()
+llvm_test_executable(fdrmode-bench fdrmode-bench.cc)
+target_link_libraries(fdrmode-bench benchmark)
diff --git a/MicroBenchmarks/XRay/ReturnReference/CMakeLists.txt b/MicroBenchmarks/XRay/ReturnReference/CMakeLists.txt
--- a/MicroBenchmarks/XRay/ReturnReference/CMakeLists.txt
+++ b/MicroBenchmarks/XRay/ReturnReference/CMakeLists.txt
@@ -1,14 +1,12 @@
-check_cxx_compiler_flag(-fxray-instrument COMPILER_HAS_FXRAY_INSTRUMENT)
-if(ARCH STREQUAL "x86" AND COMPILER_HAS_FXRAY_INSTRUMENT AND NOT TARGET_OS STREQUAL "Darwin")
-  # retref is currently failing on Darwin.
-  #
-  # ld: in section __DATA,xray_instr_map reloc 0: X86_64_RELOC_SUBTRACTOR must
-  # have r_extern=1 file
-  # 'MicroBenchmarks/XRay/ReturnReference/CMakeFiles/retref-bench.dir/retref-bench.cc.o'
-  # for architecture x86_64
-  list(APPEND CPPFLAGS -std=c++11 -Wl,--gc-sections -fxray-instrument)
-  list(APPEND LDFLAGS -fxray-instrument)
-  llvm_test_run()
-  llvm_test_executable(retref-bench retref-bench.cc)
-  target_link_libraries(retref-bench benchmark)
-endif()
+# ReturnReference is currently failing on Darwin.
+#
+# ld: in section __DATA,xray_instr_map reloc 0: X86_64_RELOC_SUBTRACTOR must
+# have r_extern=1 file
+# 'MicroBenchmarks/XRay/ReturnReference/CMakeFiles/retref-bench.dir/retref-bench.cc.o'
+# for architecture x86_64
+
+list(APPEND CPPFLAGS -std=c++11 -Wl,--gc-sections -fxray-instrument)
+list(APPEND LDFLAGS -fxray-instrument)
+llvm_test_run()
+llvm_test_executable(retref-bench retref-bench.cc)
+target_link_libraries(retref-bench benchmark)